Introduction: Why CAD?

CAD stands for Computer-Aided Design. It
is a generic name for software used by people like engineers and architects
to draft projects like machines and buildings. CAD programs are the
virtual "drawing boards" of today: geometrically oriented
and very precise.

To develop quilts and images of quilts, I make frequent use of AutoCAD
LT*, which is the "Lite" version of the regular AutoCAD*,
a market-leading software package from Autodesk*. It offers most of the features
of its larger brother but costs only a fraction of the price. Although
that is still more than you pay for the average quilt design program,
I think the investment is well worth it. AutoCAD LT can be purchased
in software stores and through software catalogues.

AutoCAD LT is not specifically targeted to quilters and lacks the typical
goodies like libraries of blocks and fabrics, yardage calculation and
a quilter-friendly interface. But once you get the hang of it, you will
find it to be a powerful and versatile tool to develop quilts, from
the first stage to the last, from traditional to innovative. To list
just a few design elements and quiltmaking tools it brings within your
grasp:

A strong side of AutoCAD LT is customization. It allows the user to
manually access, alter and exchange the basic elements that constitute
a design. To me, this approach by far outweighs the shortcomings it
may possess in comparison with quilt development software.

Getting started

The program version on which this article is based is AutoCAD LT Release
2 for MS Windows* 3.1x. There are newer, more advanced versions on the
market, but that should not cause any confusion here, for I describe
only some of the essential commands, which are, as far as I know, the
same in every version.

The minimum system requirements to run AutoCAD 2 for MS Windows 3.1x
are:

MS DOS* 3.31 or later (5.0 or later is recommended).

Windows 3.1, running 386 Enhanced Mode.

386, 486 or Pentium-based system with a math coprocessor.

Mouse or pointing device.

8 Megabytes of RAM (recommended).

16 MB of free hard-disk space.

When you boot up AutoCAD LT, you will see a window with the following
contents:

Drop-Down menus at the top of the screen.

A work sheet area where the objects are drawn.

A Toolbar with command buttons, at the top of the worksheet
area.

A movable Toolbox with more command buttons.

A keyboard command line at the bottom of the work sheet area.

Commands. The commands to change settings and generate
or manipulate drawn objects can be entered by clicking with the mouse
on the command buttons, by typing them in the command line or via drop-down
menus. In this article, all AutoCAD LT command names are shown in capitals,
e.g. DDRMODES, COPY, OFFSET. In this section, I introduce a few commands
to set up your work sheet for quilt design. They give you an impression
of the powers you hold when working with AutoCAD LT.
To exit a repetitive command, like multiple copying, press the right
mouse button or the ENTER key.
To repeat the last command do the same: press the right mouse button
or the ENTER key.

DDLMODES
This command activates the Layer Control dialog box and allows you to
generate layers on which to place the elements of a drawing. By turning
individual layers on or off, freezing/thawing them or locking/unlocking
them, you can activate and de-activate the objects placed on them in
various ways.

Disregard the other boxes. Click on OK. Now you have a snap-on grid
of squares that measure 1 x 1 Unit. These Units are relative, based
on Floating-Point calculation. Their absolute lengths can be determined
in the Print/Plot menu window. I will return to this further below in
this section.

The work sheet area shows the grid as tiny black dots. They are the
gridpoints, where the imaginary horizontal and vertical gridlines intersect.
For reasons of clarity, I show these gridlines here in light grey instead
of displaying the gridpoints. For an example, see Figure 1.

LIMITS
The work sheet has a rectangular shape. You can change its relative
dimensions by entering new Limits values for the Lower left corner and
the Upper right corner of the work sheet. The LIMITS function wants
you to type these new values at the command line, in the form of two
sets of co-ordinates, which correspond with the relative Units (see
DDRMODES). For instance, if you define "Lower left corner"
as "0,0" and "Upper right corner" as "35,25",
you will have an area of 35 Units wide and 25 Units high on your screen,
a nice setup for drafting small quilts. At any moment during a session,
you can change these dimensions with the LIMITS command.

ZOOM
This command allows you to enlarge a part of a drawing on your screen
to get a better hold of small objects. If you want to zoom out to the
previous screen again, enter ZOOM and then "p" in the command
line. If you want to view the whole screen as you last defined it with
the LIMITS command, enter "all" instead of "p".
The command ZOOM does not affect the actual size of the objects.

UNDO
A drawing session is nothing but a string of commands. During each session,
AutoCAD LT maintains a temporary history list of this string. This is
convenient at moments when you discover that your project is going the
wrong way and you want to bring the drawing back to a state from where
you think you can continue in order to reach your goal. You do this
by repetitively entering the command UNDO, which every time removes
and neutralizes the most recent command in the history list.
When you exit the program, the history list is gone. The drawing is
saved in AutoCAD *.DWG format. When you open the drawing again, a fresh,
blank history list is opened along with it that keeps track of the commands
you use during this new session.

PLOT
This is the print command. It activates the Plot Configuration dialog
box to prepare the drawing for printing and to set up your printer or
plotter. The most important options at this moment are:

- "Print/Plot Setup & Default Selection...", to
tell AutoCAD about the printer you use.
- "Inches" and "MM", two radio buttons
to choose English or Metric as the unit of measurement.
- "Plotted Inches (or MM) = Drawing Units", to set the absolute
length of the relative Unit.
- "Preview", to preview your drawing and its positioning
on the paper.

The absolute length of the relative AutoCAD Unit is crucial when you
make piecing or appliqué templates or quilting stencils. I usually
combine a grid with squares of 1 x 1 Units (see DDRMODES) with corresponding
absolute values of 1 inch to 1 Unit.

DXFOUT, PSOUT, WMFOUT
Use these file export commands to make drawings legible to programs
that do not recognize the standard AutoCAD *.DWG format.
DXFOUT exports a drawing into a *.DXF (Drawing Exchange Format) file,
which can be imported in graphic design environments such as CorelDRAW!*,
and further processed.
PSOUT exports a drawing into a PostScript file, which is a common format
in the desktop publishing world.
WMFOUT exports a drawing into a *.WMF (Windows Metafile Format) file,
which can be incorporated in MS Windows environments such as MS WORD*.
I publish some of my commercial patterns
in this way.

In the following sections of this article, I will describe three small AutoCAD
projects for quilters, in which I introduce some basic drawing commands. To make
it a bit more exciting, I will focus on curved lines. The Projects are the following:

They are meant
to give you an idea of what you can already do with just a few commands at hand.
The User's Guide that comes with the program will help you further; it
is one of the clearest software manuals I have come across. I strongly suggest
AutoCAD users to consult it in conjunction with this article, because it provides
valuable command shortcuts and helps prevent pitfalls beginners are easily dragged
into.

The goal of the first Project
is to create a graphic, black-and-white draft of the following square Potholder
design:

Figure 2
Applecores Potholder

Applecores, also known as
Double Axes or Friendship Curves, are patches with four curved sides. The Potholder
shown in Figure 2 has twenty-five of them: nine whole ones in the middle,
twelve half ones at the edges and four quarter ones in the corners. The narrow
reddish frame around the design represents the binding.

Anatomy of
Applecores. The light-green colored Applecores are vertically oriented,
while the darker green ones between them lie horizontally. Yet they are of the
same shape, with two opposite sides "caving in" (concave) and the other
two "bulging out" (convex). The concave sides of the light green Applecore
patches are the convex sides of the dark green Applecores, and vice versa. In
other words, the Applecores pattern is a pure tessellation, or tiling, of seamlessly
interlocking copies of one and the same shape. Every side is one-fourth of a circle.
When you extend the sides to make the circles complete, you see the following
interlacing pattern of circles emerge:

Figure 3
Anatomy of Applecores

The outlines of the Applecores
are shown in black, the remaining parts of the circles in lavender. The circles
intersect at regular intervals that are marked by gridpoints of the grid of squares.
Notice that in every Applecore, the two opposite sides that are "bulging
out" belong to one and the same circle. Another interesting detail: the lavender-colored
circle arcs are, too, a continuous pattern of Applecores.

Drafting
an Applecore. First I set up a grid of snap-on squares like I described
in the previous section under DDRMODES. To create the "atom" of an Applecore,
the curved side, I need to have a circle of the right size. In our current project,
the circle touches the four points of a square made of two by two gridsquares.
I Enter the command CIRCLE. AutoCAD asks me to pick a point as its center (the
gridpoint marked "C" in Figure 4, left). Having made sure that
I am working in SNAP ON mode, I click on a randomly chosen gridpoint in the work
sheet area to define it. Now AutoCAD requires me to click on a second point to
mark the length of the Circle's radius (the purple line "r" in Figure
4, left). I click on the opposite corner of one of the four gridsquares that
touch the center. In Figure 4 (left), I picked the lower left gridsquare.

Figure
4 Drawing the whole Circles

To re-create the interlacing
pattern of Circles, I use the command COPY and click on the circle as the object
to be copied. I need five Circles to draw my Applecore. Therefore, I choose the
option "Multiple" ("m"), so that I can make more than one
copy of the Circle. I position the five new Circles as shown in Figure 4
(right). Then I press the right mouse button or the ENTER key to exit the COPY
command.

I now have the "raw material" to distill the four sides
of my Applecore from. The next step is to remove the excess lines. This is
done with the command TRIM. AutoCAD asks me what object to use as the cutting
edge and I click on the Circle in the middle of the group. Then AutoCAD lets me
pick out the objects to be trimmed and I simply click on those parts of the four
other Circles that are outside the central Circle, in succession. (marked by "x"
in Figure 4, right).

Figure 5 Trimmed Circles, the four Circle Arcs and an Applecore

With the trimming done (Figure 5, left), I remove
the central Circle (Figure 5, middle): it only had to serve as the cutting
edge. Now I have four Circle arcs, each one pointing in a different direction.
To get my Applecore, I use the command MOVE to bring the lower arc up by two Units
(gridsquares) and the upper one down, also by two Units (Figure 5, right).
Because I have kept my Snap mode on all along, the arcs land exactly there where
I want them to be.

Drafting the Potholder. The Applecores
Potholder consists of the same Circle arcs as described above, as well as straight
lines that mark the edges of the design.

First, I use the command COPY to
make multiple copies of the four Circle arcs and create a field of Applecores
(Figure 6). The command SNAP ON, which enables the Snap mode, ensures exact
positioning of the copies.

Figure
6 Drawing a field of Applecores

Then use the command
LINE to draw a square of eight by eight Units (Figure 7, left). After completing
the square, I exit the LINE drawing mode by pressing the right mouse button or
the ENTER key.

The straight lines cut the Circle arcs at the edges of the
design in half. To remove the outer halves I apply the TRIM command, with the
straight lines functioning as the cutting edges (Figure 7, right).

Figure
7 Trimming away the excess lines

Now that I have
completed the "Body of the Potholder", so to say, I proceed with drafting
the binding. I want it to be a quarter of an inch wide and since I have decided
that my AutoCAD Unit is going to be one inch long, I need to draw the outer edges
of the binding one fourth of a Unit away from the Body. With my current Snap
mode of one Unit enabled, I cannot access the spaces between the one-Unit gridpoints,
so I need to adjust my Snap settings. With the command DDRMODES, I call up the
Drawing Aids dialog box:

- I keep the "On" box under "Snap"
checked. - In the box "X Spacing", I replace "1"
with "0.25". - In the box "Y Spacing", I replace
"1" with "0,25".

I keep the "Grid" settings
unchanged and click on OK. My work screen shows the same Grid division of one
by one Unit, but I can move my mouse pointer across it at intervals of one fourth
(0.25) of a Unit. With the command LINE, I draw the outer edges of the binding,
with nicely mitered corners:

Figure 8 Applecores Potholder, finished draft

My
drawing measures 8½ inch by 8½ inch. To print it exactly to size,
I enter the PLOT command. In the Plot Configuration dialog box I enter the value
"1" both for "Plotted Inches" and "Drawing Units",
to print my Potholder draft exactly to scale. But before I click on OK, I suddenly
realize that my Letter-sized paper is not large enough to accommodate the entire
drawing. So I change the "Plotted Inches" value to 0.5, thereby reducing
the dimensions of the drawing by one half. My printer gives me a picture that
measures exactly 4¼ by 4¼ inch.

Suppose I like doing things
the hard way and want to make separate templates for all the four different kinds
of patch shapes in my Applecores Potholder. They are the whole Applecore (Figure
9, patch "A"), the half Applecore cut lengthwise (Figure 9,
patch "B"), the half Applecore cut crosswise, through the waist (Figure
9, patch "C") and the quarter Applecore, cut both lengthwise and
crosswise (Figure 9, patch "D"). In Figure 9 they are
shown as templates, with seam allowances added:

Figure 9 Piecing templates for the Applecores Potholder

The light grey lines are the future seamlines. This means that
the spaces enclosed within these lines are the actual patches as they will appear
in the finished quilt top and that the areas outside them are the seam allowances.
In AutoCAD I can create seam allowances that are exactly a quarter of an inch
wide everywhere, regardless the outlines of the patch: square, rectangular, triangular,
polygonal or even with curves like in an Applecore.

Lines and Polylines.
The secret of adding seam allowances lies in the proper formulation of the seamlines
in the template. They need to be welded into a single, self-contained object,
as opposed to a collection of loose lines and circle arcs like the ones that make
up the Potholder draft from Project 1. Simple lines generated with the LINE command
won't do the job; the situation calls for a more powerful tool named Polylines.
Unlike a regular Line, a Polyline can comprise more than one element. It
can consist of several straight lines and circle arcs and still be a single object.
Such constituent elements are called vertexes and they are linked together through
nodes like the shackles in a chain. When this "chain" forms a continuous
circuit like a bicycle chain, the Polyline is defined as "closed". Thus,
if the four circle arcs of an Applecore are connected by nodes all around, the
Applecore is a single, closed object.

In Figure 10, I show how I
draw the four Applecore patch shapes, in three steps.

Figure
10 Drafting the patch shapes

Step 1 (Figure
10, top). I draw the circle arcs and straight lines, which are the "atoms"
of the patch shapes, on a grid with the Snap mode enabled. The Snap value and
the Grid value are both set to "1". Circle arcs can be converted into
Polyline vertexes, but regular straight Lines cannot. To draw them, I use the
PLINE (Polyline) command instead of LINE. AutoCAD asks me to set the starting
width and the ending width of the Polyline, but I simply press the ENTER key,
thereby maintaining the default width "0". As a result, my Polylines
will be printed in their minimum width, rendering my paper templates as precise
as can be. Every time I finish a Polyline, I press the ENTER key to exit the PLINE
command..

Step 2 (Figure 10, middle). With the help of the
command TRIM, I remove the excess bits of circle arc outside the patch shapes.
Then I press the ENTER key.

Step 3 (Figure 10, bottom). Using
the same command TRIM, I remove the excess bits of straight Polyline outside the
patch shapes. Then I press the ENTER key.

Closing the Polylines.
My patch shapes now consist of the proper Polyline vertexes but these aren't connected
into closed objects. The arrows in Figure 11 tell where the "loose
joints" are located. You don't see the "loose joints" themselves
in the picture, but they are there all right. Notice that in the quarter Applecore
(bottom right), the two straight lines are already connected by a node (no arrow).
This happened when I drew them as a single object within one PLINE command.

Figure
11 "Loose joints"

To perform the closing, I
type the command PEDIT (Edit Polyline). AutoCAD inquires which Polyline needs
to be edited and in response I click on one of the circle arcs of the top left
patch shape in Figure 11, which is the whole Applecore. AutoCAD now presents
a choice of options and I select "j" for "Join". Then, with
my SHIFT key down, I click on all four circle arcs of the shape to select them
as a group. Finally, I press the right mouse button or the ENTER key. My Applecore
is now a closed Polyline. By pressing ENTER again, I exit the PEDIT command. To
proceed with closing the next patch shape, I type PEDIT again or simply press
ENTER to re-activate the previous PEDIT command.

Tip:
To verify whether a Polyline is closed, type PEDIT and select the Polyline in
question. If AutoCAD's first option says "Open", which is used to un-close
the polyline, then the closing has been succesful. If it says "Close",
there are still "loose joints" to be dealt with.

Outward
offsetting. It's time to draw the seam allowances. This is done with the
command OFFSET (Figure 12).

Figure
12 Offsetting the patch shapes

In the command line, AutoCAD
tells me to determine the desired distance through which to offset and I enter
"0,25". Then it asks me to select an object and I pick the top left
one, the whole Applecore. The next query is "Side to offset?" and in
response, I click on a randomly chosen point outside the patch shape. Now
my whole Applecore is finished and AutoCAD wants to know which object is next.
So I repeat the process until all four shapes have seam allowances. Then I exit
the OFFSET command. Like the patch shapes, the newly generated objects (shown
in purple in Figure 12; arrows added for visualization of the offsetting
process) are closed Polylines.

Tip: In order
to reach the objects more easily with the mouse pointer during offsetting, you
can turn the Snap mode off.

The templates are finished
and I am ready to print them out. I enter the PLOT command and in the Plot Configuration
dialog box I make sure that the values of "Plotted Inches" and "Drawing
Units" are both "1". Then I click on OK.

I carefully cut
out my printed templates and paste them on a sheet of plastic or dense cardboard.
As a matter of fact, some companies that issue precision templates for patchwork
use AutoCAD to draft them.

My square Rail Fence
design is simple and straightforward, in only two colors and without any border.
The color division of the twenty-five Rail Fence blocks make the quilt top appear
like a field of tessellating (interlocking) dumbbells, each consisting of three
bars of the same color. I want to enhance this notion of tessellation through
quiltwork and decide to do so with a pattern of curves that follow the repetition
of the dumbbells. In Figure 13, the quilting is shown in teal-colored lines:

Figure 13 Rail Fence design with fancy quiltwork

Anatomy
of the quilting pattern. The intertwining curves may look intricate and
hard to grasp, but the pattern is entirely based on one simple elliptical form.
Figure 14 shows a part of the quilt design projected on a grid of squares.
The Rail Fence blocks measure twelve by twelve gridsquares (Units) and the patches
four by twelve gridsquares (Units). Their outlines are drawn in black. The quilting
curves are teal.

Figure
14 Anatomy of the fancy quiltwork

One of the curves is
highlighted in green. This single curve is all I need to draft my quilting template.
The purple dots mark the gridpoints it intersects. The deep purple dots are positioned
at the four corners of one Rail Fence block; the lower two are also the endpoints
of the curve. To trace the quilting pattern on my quilt top, I will only have
to move my one-curve stencil about the blocks and turn it at ninety-degree angles.

Drawing
an Ellipse. AutoCAD defines an Elllipse as a circle, but with a difference
between the vertical and the horizontal diameter. The Ellipse that I need as a
basis for my curve is eighteen Units wide and eight Units high:

Figure 15
Drawing the Ellipse

I enter the command ELLIPSE and type
"c" to pick a gridpoint as its center ("C" in Figure 15).
My "Axis endpoint 1" is the gridpoint located four Units above the center
("E1" in Figure 15) and my "Axis endpoint 2" is nine
Units to the left of the center ("E2" in Figure 15). The finished
Ellipse is shown in green.

Drafting the quilting stencil.
The quilt top measures five by five Rail Fence blocks, or sixty by sixty Units.
I want it to be a small wallhanging of thirty by thirty inches, so I count a half
inch for every Unit. Determining the absolute measurements is important at this
stage, because the width of the curved slit to be cut out of the stencil sheet
depends on it.

I want the slit to be an eighth of an inch wide (0.125").
Using the OFFSET command (see Project 2), I enter the distance value of 0.125
and then offset my Ellipse twice, once to the intside and once to the outside
(Figure 16; purple arrows added for visualization of the offset process).

Figure 16 Offsetting the Ellipse inwards and outwards

The
offset ellipses, shown in purple, are 0.125 + 0.125 = 0.25 Units apart. That is
an eighth of an inch, due to the fact that in this Project, my gridsquares are
a half inch high and wide instead of one inch. In other words, my printed quilting
stencil draft will show a slit of 0.125" (an eighth of an inch) wide.

As
the next step, I draw small auxiliary lines (shown in purple in Figure 17)
that intersect the endpoints of my curve (the lower two deep purple dots in Figure
14). They serve as the cutting edges to remove the section of the ellipse
caught between them, with the help of the command TRIM. I also draw two tiny circles
with a radius of 0.125 Units, to mark the upper two corners of the Rail Fence
block (compare the upper deep purple dots in Figure 14):

Figure 17 Trimming the offset Ellipse; adding points for positioning

My draft is completed. With the PLOT command I call up the Plot
Configuration dialog box and adjust my absolute measuring values: "0.5"
for "Plotted Inches" and "1" for "Drawing Units".
When my printout is done, I paste it on a plastic quilt stencil sheet and trace
the slit and the two small circles with a burner (or double-bladed hobby knife).
The end result looks like this:

Figure
18 The finished quilting stencil

The stencil has all
the elements required for marking my quilt top: the curved slit and the four points
to align it with the corners of the Rail Fence blocks.

A note on web images.
All images in this article were drawn in AutoCAD LT Release 2 for MS Windows 3.1x.
and exported to *.DXF files using the DXFOUT command. They were imported in CorelDRAW!
and colored; all colored fields are closed Polylines generated in AutoCAD LT.
From there, they were exported as *.GIF files. It is these *.GIF pictures that
you are looking at.

Figure 19 Can your quilt design program do this?

Without
the help of a program like AutoCAD LT, I wouldn't have been able to publish my
patterns the way I wanted them, or share my quilt designs on the Internet. With
the exception of a handful, all images on my website
began their career as AutoCAD *.DWG drawings.